you could unlock this feature on your license, I believe this is the only obstacle that still prevented many providers and q work provider and others I know to use any SXT (among others) as AP,
while other competitors there is no such limitation and I believe this would be a great advantage to you because I believe that people buy more devices than exchange License
There are sxt devices with l4. Anyway I would like mikrotik to stop distinguishing the license levels too. But it is their business decision and you can freely choose what is better for you.